Around a fifth of male roach sampled in British rivers showed signs of mutating into females as a result of endocrine disrupting chemicals. Image: myfrozenlife | Flickr Creative Commons

Some chemicals in freshwater ecosystems have the potential to alter the hormonal balance and function of aquatic organisms. Such ‘endocrine disrupting chemicals’ (or EDCs) can significantly affect how aquatic organisms live, feed and reproduce, and potentially cause stress on their populations.

EDCs – which include ibuprofen (a common painkiller), progesterone (used in contraceptive pills), and numerous other steroids, pharmaceuticals and organic compounds – are increasingly pervasive in freshwater ecosystems, as a result of their widespread human manufacture, use and waste.

In 2008, Tyler’s research found that nearly a quarter of male roach sampled from 51 sites on English rivers showed signs of becoming female. These physiological changes – such as the fish having eggs in their testicles – were attributed to heightened concentrations of oestrogen (derived from contraceptive pills, and passed through the sewage system) in the river waters.

According to the authors of the new Biological Reviews review, the multiple non-lethal effects that growing numbers of EDCs can have on freshwater organisms at different scales makes their assessment and management difficult. They argue that EDC research on their effects should take place at broader spatial and temporal scales than the current laboratory centred experiments.

Such broader-scale research has the potential to reveal both direct and indirect EDC effects at individual, population and food web scales in ecosystems, they argue. This could form the basis for environmental managers and policy makers to make more informed decisions about freshwater conservation and restoration.

“A large array of substances derived from industry, drugs and personal care products can pose an environmental risk to the normal hormone functions of a wide array of organisms: These so-called ‘endocrine disrupting chemicals’ (EDCs) occur increasingly in streams, lakes and rivers, and have become a source of considerable concern because of possible effects on fish, other wildlife and, potentially, people.

So far, much of our understanding is from laboratory toxicological studies that don’t capture the complex pathways or mechanisms through which EDCs affect real ecosystems. Our review identifies the need for greater efforts using ecologically oriented assessments at population-, community- and food web levels under real conditions.”

“One of the greatest environmental success stories over the last few decades has been the restoration of urban rivers affected by gross pollution and heavy industry. However, we’re increasingly realising that complex substances like EDCs might cause continuing problems because they’re not removed fully by conventional wastewater treatment. (See, for example, Steve’s research on dippers).

Rural environments are also at risk – for example where various pesticides and pharmaceuticals from livestock reach streams and rivers. These chemicals add to the suite of multiple stressors that have to be addressed to protect and restore biodiversity and those ecosystem services for which water is critical.”

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